Numerous chewable toys for animals fabricated from rubber, plastics, rawhide and the like have long been available for the purpose of massaging the gums and strengthening the teeth of the animal, but each such toy has been subject to various objections, such as the inherent bad taste of rubber, susceptibility to destruction when chewed, and hardness or brittleness, as for example when made from Nylon.RTM. which could damage the animal's teeth. The rawhide "bone" has been in common use, but it disintegrates rapidly when chewed, and like some of the plastics used heretofore, large sections can be torn away and if swallowed can get caught in the dog's throat.
An important object of the present invention has been to provide an improved durable chewable toy or "bone" for pets, which avoids the above-noted objections, which may be molded from polyurethane to simulate a real bone having an elongated body with enlarged bifurcated ends to provide chewing protuberances for small dogs and curved exterior surfaces adapted to conform to and massage the gums of larger dogs, and wherein the elongated body curves in opposite directions from its mid-region to effect oppositely directed compound or three-dimensional curvatures, which in cooperation with the enlarged ends prevent accidental swallowing of the simulated bone by large dogs.
Another object is to take advantage of the unique physical properties of polyurethane to provide such a toy, which can be a ball or other shape as well as a simulated bone in appearance and which is molded from an elastomeric polyurethane to provide a super-tough toy highly resistant to chewing and in fact essentially indestructible by chewing except by very large dogs, wherein the polyurethane itself is odorless, tasteless, and chemically inert in the digestive system so as to be harmless if swallowed. The polyurethane has a moderate hardness durometer to assure the desired flexibility and compressibility in a chewable toy, so as to massage a pet's gums without undue wearing of the teeth and to provide a toy that can be caught in the air by a dog for example without breaking the dog's teeth, in contrast to similar bones of hard material such as Nylon.RTM. which can chip a dog's teeth. On the other hand, the polyurethane also has large coefficients of tensile strength and resistance to shearing to enable the toy to be stretched twisted and compressed within the limits of its elasticity by sharp teeth and strong jaws without disintegrating while being chewed, so as to outlast comparable toys of rubber, rawhide and even Nylon.RTM., and has the resiliency to enable return of the toy essentially to its undeformed condition after being chewed.
Another object is to provide a molded polyurethane toy or "bone" of the above character impregnated with air bubbles so as to be lighter than water and useful for example in water games with a dog or for training a dog to retrieve. Although the aerated bone is more readily destroyed by chewing, it is somewhat softer and more spongy and is thus ideal for older dogs.
Another object is to provide an improved chewable polyurethane toy of the above character having a surface-migrating flavoring agreeable to the animal and uniformly distributed throughout the volume of the toy, whereby as the surface flavoring is removed during the chewing process, the flavoring is replaced at the surface by flavoring from the interior of the toy.
Another object is to provide an improved method of manufacturing such a toy wherein an aromatic extract such as catnip or a meat flavoring is added to and uniformly distributed throughout the polyurethane material to comprise a homogenous portion of the toy.
Another and more specific object is to add the aromatic flavoring extract during the initial formulation of the polyurethane, whereby the extract is thoroughly mixed with the components of the polyurethane, first during the mixing of said components during the initial formulation, and thereafter during the granulation and mixing of the polyurethane in preparation for the final moldingoperation. By virtue of the foregoing, a thorough mixing of the extract within the polyurethane is assured and the necessity of providing a specific mixing procedure for mixing the extract within the polyurethane is eliminated. Inasmuch as the components in the formulation of the polyurethane must be thoroughly mixed in any event, the same mixing procedure is utilized both for mixing the polyurethane components with themselves and for mixing the extract with the components. The flavoring extract is usually highly concentrated, such that thorough mixing is important. Otherwise localized concentrations of the extract can overpower the sensory nerves of the animal and effect a disagreeable reaction rather than the intended taste or aroma that is pleasing to the animal.
Where the extract loses its aroma or flavor in consequence of heating, the flavoring extract is initially added and thoroughly mixed with the granulated polyurethane when the latter is heated and melted immediately prior to the molding operation. A satisfactory distribution of the extract can be accomplished by such a procedure and the extract is only subjected to a single heating cycle, i.e., the heating required to melt the polyurethane prior to the molding. The extract is spared the heat of the exothermic reaction resulting from mixing the aforesaid components during the formulation of the polyurethane.
In some conventional molding operations, the polyurethane comprises two or more liquid components that are mixed by being fed simultaneously at measured rates directly into the mold. In such instances the liquid flavoring extract is likewise fed into the mold along with the liquid components to effect a thorough mixing of the liquid extract and components for the polyurethane in a single mold filling operation.